Engine returns to idle VERY slow...HELP!

[masospaghetti]

Hey all, I have a 2000 Ex with the 4.0 OHV and 5-speed manual shift. 107,500 miles. My idle speed, even when hot, sometimes "hangs up" and takes forever to get to 600 rpm (although it always does, eventually). I thought it was the IAC valve, since I also have a strange humming noise at around 1200 rpm, but cleaning the IAC and then replacing the IAC with a new unit didn't change anything.

No check engine light.

Any ideas? Thanks!

 

[masospaghetti]

pleeeeeese? any ideas at all? are ALL 5-speed manual shifts like this?

 

[Rogers-Explorer]

maso,

I have the same problem with mine (4.0L OHV, 5sp Manual). I have cleaned the IAC, MAS, TB, Plenum, etc... I did the TPS mod a little while back and found that it helped a little, as well as giving it a Seafoam treatment. I am getting P0171/74 codes periodically (less frequently post-intake gasket replacement) and still have the high idle issue, but mine rarely drops below 900rpm. I was just content to get it down to below the 2000rpm it was idling at a few months ago.

I have a gut feeling it has something to do with the TB or TPS as it seems to be sticking a bit. Mine will drop its idle quicker by giving a little shot of gas (like the automatic choke on my '72 Comet). I've asked about taking the TB apart and giving it good going over, but didn't have any replies. (Ford manual says not to touch the Throttle Plate because it has a coating on it, and I just want to know if this is true).

Good luck.

Cheers, Roger.

 

[Hoppy]

I had this problem on my old 92 ex about 6 year ago. The TPS was gone, but I also had a code come up on it. I replaced it and the problem went away, but I also tested the old sensor and found it to stop continuity between two of the terminals while turning the contact. Not sure if this is it, but it worked after replacing it.

 

[masospaghetti]

Thanks for the replies.

I just cleaned my MAF and throttle body, as well as checking my TPS -- it showed 0.98 volts. Although, I'll admit, I didn't see if they're were any discontinuities. I used to get the p171/p174 codes as well and I found that 3 of my upper intake bolts were loose, and haven't gotten it since.

At least a new Neihoff TPS is only $26.99. I hate to throw money at a problem though without really knowing what the problem is.

Could it a vacuum leak?

 

[Hoppy]

Now that I think of it, and I don't have an OHV 4.0 any more, but I recall my 92 Ex and my Uncle's old 98 with the OHV, just for the hell of it, and because I heard of the upper intake causing coolant loss, I re-torqued the lower intake on them. Low and behold, they were both not tight. Not loose however, but when I tightened them you could tell that they needed a bit of tightening. After tightening the first time on my old 92 I got rid of some, but not all of the coolant loss. I have never tried to tighten the lower intake on my 00 ex, but it is a SOHC engine and have not had one aiota of a problem with it at all, but it only has 130,000 km on it and am not sure I want to tinker with it yet because of no problems with it.